A trend in the gaming industry has been to use PC technology where possible instead of proprietary custom hardware and software. The Gaming Standards Association (GSA), an USA association of gaming machine manufacturers, peripheral manufacturers and operators, has been working towards standardising a communication protocol between a controller of an electronic gaming machine (EGM) and its peripherals based on universal serial bus (USB) technology, called B-Link. The intent is to standardise communication for virtually all peripherals in the EGM. Currently work is active on the coin hopper, bank note acceptor, coin acceptor, and printer.
Traditionally, EGM's have been custom designed to meet the specific requirements of gaming regulations promulgated by gaming control authorities. One important requirement is to maintain the integrity of critical data when the EGM loses power.
Critical data includes accounting information (known as meters) stored in battery backed static random access memory (SRAM), also referred to in this specification as meter RAM. Such memory chips have, to date, been directly interfaced to the main CPU of the EGM, enabling fast access to meter RAM. To comply with gaming regulations such as those in Australia, redundancy in the meter RAM has been used. For example, in Australia, three meter RAM chips are used, each storing the same data. In the event of a memory corruption in a single meter RAM chip, the other two chips are used to correct and restore the data.
Some meter information is also displayed on tamper resistant electro-mechanical counters, also known as mechanical meters. These mechanical meters are visible to an auditor and show cumulative values rather than duplicating the information in meter RAM as, unlike meter RAM, the mechanical meters cannot be reset to zero.
Updates to meter RAM must be completed as a single, uninterruptible transaction (ie. atomic); such that, once the update to the meter RAM has started, it must be completed. For example, if money is moved from one meter to another, it must first be subtracted in total from one meter then added to another. To avoid the loss of money in the event of a power failure, it must not be possible for a power fail to prevent the addition of the money to the second meter once it has been subtracted from the first meter.
In the case of mechanical meters, once the meter has started clicking over from one position to the next, it must continue to do so for the time required to guarantee correct operation (typically 25 ms), otherwise when power is restored to the EGM, it is not possible to determine the actual mechanical meter value.
In a conventional EGM, the mains power supply senses the mains power input and when it is detected to be failing, the power supply generates a power fail warning to the controller of the EGM. The time between the power fail warning and the power actually failing is known as the hold-up time. What is meant by “failing” is that the power supply is outside normal operating parameters or specifications, ie. it may be that power is available but it is insufficient for the EGM to operate correctly or at all.
Once a power failure has been detected, the controller completes any in-progress updates to meter RAM and the mechanical meters and accepts no further updates. The power supply is designed to have sufficient hold-up time for the controller to shut the EGM down in an orderly manner, adding considerable cost to the power supply.
An important effect of the change from custom hardware and software to standard PC technology is the lack of control in the response time of the controller to external or peripheral events. The GSA B-Link standard recognises this problem and, rather than customise the PC standard hardware/software to meet these real-time requirements, the standard changes the requirements of the peripherals and peripheral communications protocols. Critical peripherals store the critical data sent to the EGM controller, even over power down/up, until its receipt has been acknowledged by the EGM controller.
Jackpot controllers interface to a number of gaming machines and provide a network based prize. Jackpot controllers require data to be reliably stored over the power failure interval.